A Shrewd Proposition - peaceful solution - is it possible?

[Tündérdöme]

Hello guys!
According to the official Pillars of Eternity 2 Wikia , there is a peaceful solution of the quest "A shrewd proposition".
"Alternate - Confront Kua with evidence of illegal slaving"
So, as it sais, you can confront Master Kua with evidence of illegal slaving and make him leave.
Now, anyone succeeded with that? Is it really possible?
I'm pretty sure I did everything according to the above-mentioned description, but still, it doesn't work.
What have I done?

• Meet/talk with Aeldys agent (evidence #1) - check
• Go to the sea cave/prison undetected - check
• Talk with the Huana, but don't let them free yet - check
• Enter the fort peacefully - check
• Gain audience with Kua - check (I remained silent during the auction and then I gained the audience via Auctioneer Marcca)

Dialog with Kua:
1st - "Does he know you're trading illegally" - check
2nd - I told him I have spoken with the Wahaki (evidence #2)
And this is where it goes wrong.
According to the official wiki, here I will require a streetwise 5 check. Me personally has 4, but with my team's help, it should be enough. I also tried using oil of allure (+2 streetwise, which makes it 6), still with no success.
So, I just can't make him leave, there is no option to speak with him about leaving.
Did I do anything wrong? Is it really possible to make him leave?
Any ideas?
Thx